Did Moldenhawera flowers evolve through mimicry with oil-producing Malpighiaceae?

Abstract

Floral mimicry is a captivating phenomenon wherein flowers imitate traits of other plants to attract specific pollinators. The Caesalpinioideae legumes in general have relatively unspecialized flowers, which has allowed the development of disparate morphologies adapted to different groups of pollinators. This study describes the pollination of Moldenhawera nutans L.P. Queiroz, G.P. Lewis & Allkin, and explores its potential floral mimicry toward Malpighiaceae flowers. Our investigation revealed that M. nutans is pollinated by bees of the genera Centris and Xylocopa. It also presents compelling evidence supporting the hypothesis of floral mimicry, including striking similarities in floral display, shared oil-collecting pollinators, oil collection behavior in M. nutans despite the absence of oil production, and the reliance on exogenous pollen for reproduction. These findings suggest that species of Centris visit M. nutans flowers under the mistaken impression of oil availability, subsequently transitioning to pollen collection. We explored other potential cases of floral mimicry with Malpighiaceae in the Caesalpinioideae legumes by optimizing the Malpighiaceae-like floral display on a dated phylogeny of this subfamily. However, current information does not allow us to determine whether the similarities in floral morphology represent cases of floral mimicry, phylogenetic inertia, or simple convergence. Hypothesis tests are suggested that can guide the study of these fascinating evolutionary processes in the group.